Electron tube



May 30, 1933. R. sTRlGEL 1,911,976

ELECTRoN TUBE Filed Jan. 7, 1930 2 Sheets-Sheet l 0 I Kaw May 30, 1933. R. sTRlGEl. 1,911,976

ELECTRON TUBE Filed Jan. 7, 1930 2 Sheets-Sheet 2 Patented Mayan, 1933 UNITED sT-.aras

PATENT OFFICE MBEBT STBIGEL, 0F .IBERLQIyCEABLOTTENBUBG, GERMANY, ASSIGN'OR T0 SIEMENS SUHUCEBTWEBKE AKTIENGESELLSCHAFT, 0F BERLIN-SIEMENSSTADT, GERMANY,

A. CORPORATION OF GEBIANY i ELECTBON TUBE Application iled January 7, 1930, Serial No. 419,034, and in Germany January 10, 1529.

My invention relates to electron tubes, and more particularl to improvements in the arrangement of e ectron tubes for extra high voltages.

In ele`tn tubes (cathode-ray tubes) the 'formation-of positiveions can never be en- Y quence of the correspondingly increased bombardment of the cathode by ions. This increase of the electron emission may attain such a degree that labile conditions develop due to theV self-heating of the tube.

Electron or cathode-ray tubes for very highvoltages in which the stream of ions becomes particularly noticeable are generally designed in such a way that the. voltage is subdivided over a plurality of `steps in thema'nner of a cascade, and the accelerationsare `imparted to the electrons in successive stepsunder the action of the voltage. In such electron tubes for extra high voltages with subdivided voltages it has been attempted to eliminate the adverse eiects of thepositive ions by interposin between the'individualitubes 'of the cascae a metal foil andth'us 'to prevent the passage ofthe positive ions Vfrom thel end electrode of one tube to theinlet electrode of the next tube. ThismetalI foil is then permeable forthe Y electronsgto 'be further accelerated but im permeable for the positive ions.

Theinethod described has, however, considerable"fde`fects. `The metal foil impermeable for the ions` although permitting the electrons to ass also causesa loss of velocity of the e ectrons. This loss of velocity causes a considerable temperature rise of the metal foils, particularly 1n the higher steps of the voltage cascade which is lia-ble to exceed'the permissible value. To this must be added the fact that undesirable X-rays develop at the metal foil.

According to my invention the adverse el'ect of the stream of ions is eliminated without the described disadvantages being present. According to my invention the ions are deflected into diil'erent paths from those of the electrons by means of a magl netic field.

My invention is based upon the physical conditlons described in the following lines.

rIn a homogeneous magnetic field of the strengthH a massparticle of the mass fm. and having a definite velocity describes a track the curvature radius 1 of vwhich is determined by the formula wherein e is the Icharge of the particle and V the applied voltage between the electrodes. In a magnetic field of 280 gauss and a voltage of 100 kv. between the electrodes of one cascade step al curvature radius 1-=5 cm. for instance is obtained by inserting the values for the electron.

My invention is based upon the fact that the positive ions possess a mass which is by several orders larger than the mass of the electrons. The mass of the hydrogen ion, for instance, is 200() times as large as the mass of an electron. At equal potential between the two electrodes the'hydrogen ion,

velocity of the electrons, can be deflected intovv another direction than the electrons.

According to my invention I provide metal screens or bales toward which the ions are deflected by' the magnetic field while the electrons continue their 4travel in anotherA direction. The width of the velocitygspecftrum which is given free for the electrons by the deflection 4of the major portiongof the ions is determined by the constructionioigg'vtkllfeFv tube. For ions of other gases thankhfydrof gen this spectrum is located at still'r lowerA velocities.

Since the positive ions are accelerated `-in the dlrection of the cathode and thus; run

counter to the velocity of the electrons, the

ions not screened out in the preceding cascade are screened out in the next ste In order to obtain a sharp screening it 1s neoessa that the electrons` are as stronglyas ossi le concentrated prior to their entry mto the magnetic field. yThis may easily be attained bymeans of a suitably located solenoid or a combination of 'a plurality pf solenoids.

, The drawings -aixed to 101g' loillustrate a number of emb i invention, of which Fig. 1 shows, partlydiagrammatically and in longitudinal section, a cascade arrangement of two electron tubes;

Fig. 2 shows in larger scale and in longitudinal section the detail construction of the heated cathode of tube 1 in Fig. 1;

Fi 3u shows in larger scale and in longitu inal section the-separating device for the electrons and ions;

Fi 3b shows a side elevation of the device m Fi 3a partly in section;

Fig. 4 s ows a lurality of cascaded sections composing t e tube; Fig. 5 shows a referred manner of connecting the indivi ual sections, and

Fig. 6 shows a modification of Fig. 4. Referring to Fig. 1 of the drawings it will be observed that the discharge vessel consists of two glass bulbs 1 and 2 which are connected with one another by means of necks 3 and 4. The bulbs are preferably placedunder an angle of 120o to each other since it is then possible to separate suliciently the tracks of the ions and electrons and since, on the other hand, the ends of the individual tubes arranged in cascade do /not come into an impermissibly close vicinity to each other se 'that an external arcover is liable to occur.

The necks contain at the points 5 and 6 an electrode each, the potential of which lies between that of the cathode 7 and the anode 8. The electrodes 5 and 6 are formed by a small metal cylinder. The hot cathode 7, which in Fig. 2 of the drawings is shown on a larger scale, consists of an incandescent wire loop 9, and a screen 12 the object of which is to concentrate the stream or beam of electrons. The terminals of the high voltage source 13 and 14 areconnected with the hot cathode 7 and the anode 8. The source of high voltage is in the middle provided with a tap which is connected to the electrodes 5 and 6 and which carries a potential which is equal to half the value of the potential difference between the cathode 7 and the anode 8. Between the two elec- 'trodes 5 and 6 is located the device illustrated on a larger scale in Figs. 3 and 3b of the drawings and which according to my invention brings about a separation of the tracks or v,paths of the electrons and ions.

15 A is a glass tube, which connects the @5 necks 3 and 4 of tubes 1 and 2, 16 are the specification ments of my pole shoes disposed on each side ofl tube15,

The screens serve to catch the positive ions.

While the electrons flow deflected-on the path indicated in broken lines, the (hydrogen) ions the velocity Aof which does not lie around 2.2 per cent of the electron velocity are arrested by the screens or baile plates 20, those of higher velocity by the screen at the outside,.those of lower velocity by the screen at the inside of the bend. 21, 22, 23 are solenoids surrounding the pertaining tube necks and serving for the concentration of the electron beams.

Preferably a defeating deviceshould be provided just behind the cathode, as shown' in Figs. 4 and 6, since in this way the cathode can be protected most effectively. In Fig. 4 an electron tube with cascaded sections is shown which, besides the deiecting device for the protection of the cathode, is

equipped with three further deflectors the direction of the bend of which changes. In this way it is possible to construct the tube in a main direction. According to the requirements of the application of the tube, the cathode, .the intermediate electrode and the anode may be brought to the potential zero.

In Fig. 5 of the drawings is illustrated the design of an electron (cathode-ray) tube composed of cascaded sections and according to my invention, which results in a particularly satisfactor arrangement composed of the individua tubes. In such an arran ement the individual sections of the casca e may be separately evacuated and transported, and thus at site only assembly 1s necessary.

As will be seen from this ligure, 3 and 4 are again the endsof'the glass bulb necks of the usual evacuated'tubes already adjusted at site. They are separated by the glass partitions 24 and 25 and possess tubular extensions 26 and which are now fused together and provided with a lateral connection 27 by blowing. The T stud 27 is connected to a high-vacuum pump by the pump branch 29 through the trap 28 for liquid air. During the pumping process the piece of tube 27 is heated to a temperature of about 500 C. The tube is then sealed at the capillary contraction 30. N ow the'glass walls 24 and 25 are destroyed. This may be effected by means of a piece of iron 31 which after the smashing o the glass is passed into the carbon bag 32 and then no longer obstructs the discharge path.

I claim as my invention: vAn electron. discharge device for high voltages wherein electrons and undesired positive ions are generated, com rising av plurality ofV individual tubes mec anically and electrically connected in series for d1- viding the `total voltage into a number of cascaded steps, and means for deflectin the positive ions and the electrons along dliferent paths, comprising the arrangement of the axes of adjacent tubes at an angle less than 180 Y to one another, and means. for producin in the apex of the angle a mag-l neticv iel in a direction parallel to a line bisecting said angle, for deiecting the ions and electrons into different aths.

VIn testimony whereof I aix my signature.

ROBERT STRIGEL. 

